The present invention relates to the field of mass storage devices. More particularly, this invention relates to a system for implementing automatic acoustic management in disc drives.
One key component of any computer system is a device to store data. Computer systems have many different places where data can be stored. One common place for storing massive amounts of data in a computer system is on a disc drive. The most basic parts of a disc drive are an information storage disc that is rotated, an actuator that moves a transducer head to various locations over the disc, and electrical circuitry that is used to write and read data to and from the disc. The disc drive also includes circuitry for encoding data so the data can be successfully retrieved from and written to the disc surface. A microprocessor controls most of the operations of the disc drive as well as passing the data back to the requesting computer and accepting data from a requesting computer for storing to the disc.
The transducer head is typically placed on a small ceramic block, referred to as a slider, that is aerodynamically designed to fly over the disc as the disc is rotated under the influence of a spindle motor. The slider is passed over the disc in a transducing relationship with the disc. Most sliders have an air-bearing surface (xe2x80x9cABSxe2x80x9d) which includes rails and a cavity between the rails. When the disc rotates, air is dragged between the rails and the disc surface causing pressure, which forces the transducer head away from the disc. At the same time, the air rushing past the cavity or depression in the ABS produces a negative pressure area. The negative pressure or suction counteracts the pressure produced at the rails. The slider is also attached to a load spring which produces a force on the slider that is directed toward the disc surface. The various forces equilibrate so that the slider flies over the surface of the disc at a particular desired fly height. The fly height is the distance between the disc surface and the transducing head, which is typically equal to the thickness of the air lubrication film. This film eliminates the friction and the resulting wear that would occur if the transducing head and the disc were to be in mechanical contact during the disc rotation. In some disc drives, the slider passes through a layer of lubricant rather than flying over the surface of the disc.
Information representative of data is stored on the surface of the storage disc. Disc drive systems read and write information stored on tracks on the storage discs. Transducers, in the form of read/write heads attached to the sliders, located on both sides of the storage disc, read and write information on the storage discs when the transducers are accurately positioned over one of the designated tracks on the surface of the storage disc. The transducer is also said to be moved to a target track. As the storage disc spins and the read/write head is accurately positioned above a target track, the read/write head can store data onto the track by writing information representative of data onto the storage disc. Similarly, reading data from a storage disc is accomplished by positioning the read/write head above a target track and reading the stored material on the storage disc. To write on or read from different tracks, the read/write head is moved radially across the tracks to a selected target track. The data is divided or grouped together on the tracks. Some disc drives have a multiplicity of concentric circular tracks. In other disc drives, a continuous spiral is one track on one side of drive. Servo feedback information is used to accurately locate the transducer head. The actuator assembly is moved to the required position and held very accurately during read or write operations using the servo information.
The actuator is rotatably attached to a shaft via a bearing cartridge which generally includes one or more sets of ball bearings. The shaft is attached to the base of the disc drive, and may also be attached to the top cover of the disc drive. A yoke is attached to the actuator. A voice coil is attached to the yoke at one end of the rotary actuator. The voice coil is part of a voice coil motor (VCM) used to rotate the actuator and the attached transducer(s). A permanent magnet is attached to the base and the cover of the disc drive. The VCM which drives the rotary actuator comprises the voice coil and the permanent magnet. The voice coil is attached to the rotary actuator and the permanent magnet is fixed on the base. The yoke is generally used to attach the permanent magnet to the base and to direct the flux of the permanent magnet. Since the voice coil sandwiched between the magnet and the yoke assembly is subjected to magnetic fields, electricity can be applied to the voice coil to drive the voice coil so as to position the transducer(s) at a target track.
Two of the ever constant goals of disc drive designers are to increase the data storage capacity of disc drives, and to decrease the amount of time needed to access the data. To increase storage capacity, current disc drives have increased numbers of tracks per inch (TPI). Put simply, current disc drives squeeze more tracks onto the same size disc. Decreasing the amount of time needed to access the data can be thought of as increasing the speed at which data is retrieved. Increasing the speed at which data is retrieved is very desirable. Any decreases in access time increase the speed at which a computer can perform operations on data. When a computer system is commanded to perform an operation on data that must be retrieved from disc, the time needed to retrieve the data from the disc is often the bottleneck in the operation. When data is accessed from a disc more quickly, more transactions can generally be handled by the computer in a particular unit of time.
A rotating disc data storage device uses a servo system to perform two basic operations: track seeking and track following. Track seeking refers to the ability of the disc drive and the servo system to move the read/write transducer head of the disc drive from an initial track to a target track from which data is to be read, or to which data is to be written. The settling of the transducer head at the target track is referred to as seek settling. Track following, which is performed after the head has been aligned with a target track, refers to the ability of the disc drive and the servo system to maintain the read/write head positioned over the target track. Note that, to effectively perform track seeking and track following in a disc drive with increased TPI, the servo open loop bandwidth of the system must also be pushed or increased.
While performance indices of disc drives, such as access times, WinBench scores, etc., are important concerns for customers of disc drives, another important concern is the acoustic level of disc drives. Normally, the acoustics of a disc drive includes two portions: an idle mode portion and a seeking mode portion. In the idle mode portion, the source of the acoustics is the spindle motor which rotates the disc. The idle mode acoustics form an acoustic baseline for the disc drive. In the seeking mode portion, the source of the acoustics is the VCM. The VCM seeking acoustics are added to the baseline. Customers generally prefer disc drives with low acoustics.
In practice, there exists a trade-off between the performance indices and the acoustic levels of a disc drive. In particular, to achieve faster disc drive performance, the acoustic levels of a disc drive will be increased (i.e., made noisier). Conversely, to achieve improved acoustic levels, disc drive performance will be sacrificed. The optimal trade-off between performance and the acoustic levels of a disc drive will be different for different customers. For example, in the consumer electronics market, some customers may be relatively sensitive to the acoustic levels of disc drives, and may prefer a quieter disc drive over a noisier disc drive even if it requires a sacrifice in the disc drive performance. On the other hand, other customers may be relatively insensitive to acoustic levels, and may prefer a higher-performance disc drive over a lower-performance disc drive even if it requires an increased level of acoustics. The sensitivity of still other customers to the acoustic level of disc drives may change over time. For example, a particular customer may prefer a quieter disc drive when listening to music that is stored in a digital file on a disc drive, but may prefer a higher-performance disc drive when running a spread sheet or a database program.
To meet the needs and preferences of disc drive customers, an Automatic Acoustic Management (AAM) feature set has been proposed and been added to the American National Standard for Information Systemsxe2x80x94AT Attachment with Packet Interfacexe2x80x946 (ANSI ATA/ATAPI-6) specification. This standard specifies the AT Attachment Interface between hosts and storage devices, and provides a common attachment interface for system manufacturers, integrators, software suppliers, and suppliers of intelligent storage devices. The AAM feature set will allow a host (e.g., a host computer) to select an acoustic management level for a disc drive. By using the AAM feature set, different customers (or a single customer at different times) will have the freedom to select a desired balance between the acoustic levels and the performance indices of a disc drive. In particular, by using the AAM feature set, an acoustic management level for a disc drive will be specified by a command that is sent from the host to a disc drive controller. This command will specify the desired acoustic level of the disc drive. In response, the controller will control the operation of the disc drive in a manner such that the desired acoustic level will be achieved.
Therefore, there is a need for a method and apparatus for implementing an automatic acoustic management (AAM) feature for a disc drive that allows a host to specify a balance between the performance and acoustic levels of the drive. There is also a need for a method and apparatus for implementing an AAM feature for a disc drive such as that proposed for the ATA/ATAPI-6 standard. There is also a need for a method and apparatus for implementing an AAM feature for a disc drive which is efficient in terms of its memory and/or processing requirements. There is a further need for a method and apparatus for implementing an AAM feature in a disc drive seeking operation, which can be performed for each seek or for a plurality of seeks.
In accordance with one embodiment of the present invention, a method of implementing an automatic acoustic management (AAM) feature for a disc drive includes the steps of receiving an acoustic/performance compromising factor from a host, and tuning performance of a disc drive according to the compromising factor. The step of tuning includes applying the compromising factor to at least one control parameter for the disc drive to generate at least one modified control parameter. The method also includes executing a control loop for controlling an operation of the disc drive, wherein the control loop uses the at least one modified control parameter.
In one embodiment, the executing step includes executing a seeking control loop for controlling a seeking operation of the disc drive. The receiving step and the tuning step may be performed before starting each seek, in which case the executing step is performed for controlling each seek using the modified control parameter(s) that was generated using the compromising factor received before starting that seek. The receiving and tuning steps may also be performed before starting a plurality of seeks, in which case the executing step is performed for controlling the seeks using the modified control parameter(s) that was generated using the compromising factor received before starting the seeks. The control parameter(s) may include a position gain, with the tuning step generating a modified position gain (e.g., by multiplying the position gain and the squared compromising factor). The control parameter(s) may also include a velocity gain, with the tuning step generating a modified velocity gain (e.g., by multiplying the velocity gain and the compromising factor). The control parameter(s) may also include a control effort limit value, with the tuning step generating a modified control effort limit value (e.g., by multiplying the control effort limit value and squared compromising factor). The control loop may include a velocity profile generator for generating a desired velocity based on a difference between an actual and a target position, with the tuning step modifying the desired velocity (e.g., by multiplying the desired velocity and the compromising factor). This generator generates the desired velocity using a single velocity profile stored in memory, this velocity profile used for different values of the compromising factor.
In accordance with another embodiment of the invention, a disc drive includes a base, a disc rotatably attached to the base, an actuator assembly including an arm for carrying a transducer head in a transducing relation with respect to the disc in response to a control signal, a receiver for receiving an acoustic/performance compromising factor, and a controller coupled to the actuator assembly and receiver for monitoring an actual position signal for the arm and for generating the control signal. The controller executes a control loop for controlling seeking which has at least one control parameter that is modified by applying a received compromising factor to the at least one control parameter to tune acoustic performance of the drive.
In embodiments of this disc drive, a control parameter(s) may be modified for each seek by a compromising factor received before starting that seek, or may be modified for a plurality of seeks by a compromising factor received before starting the plurality of seeks. The control loop may include a first difference element, a velocity profile generator, an applying element, a second difference element, a velocity gain element, and a limit element. The first difference element may determine a position error between the actual position signal and a target position. The velocity profile generator may generate a desired velocity from the position error, and introduce a position gain that is modified by application of the received compromising factor. The applying element may apply the compromising factor to the desired velocity to generate a modified desired velocity (e.g., by multiplying the desired velocity and the compromising factor). The second difference element may determine a velocity error between the modified desired velocity and an estimated velocity for the arm. The velocity gain element may provide a velocity gain to the velocity error to generate an unlimited control signal, with the velocity gain being modified by application of the received compensation factor. The limit element may limit the unlimited control signal to generate the control signal, with the limit also being modified by application of the received compromising factor.
In accordance with another embodiment of the present invention, an apparatus for implementing an AAM feature for a disc drive includes means for receiving an acoustic/performance compromising factor, and means for tuning performance of a disc drive according to the acoustic/performance compromising factor. The means for tuning applies the compromising factor to at least one control parameter to generate at least one modified control parameter for the disc drive.
These and various other features as well as advantages which characterize the present invention will be apparent to a person of ordinary skill in the art upon reading the following detailed description and reviewing the associated drawings.